Personal time

In Clock Anti-Clock the question is very relevant because I think it explains a situation at the end of the film where otherwise there’d be a paradox.

We hear the door knob rattle. He puts his glasses on and from then on it seems that time runs backwards from around 12:00 pm. This is inside the room where we see the clocks going backwards, and also outside where he observes people walking backwards, taps dripping upwards, etc..

By the end of the movie we have a better perspective on what’s going on outside. The ‘experienced’ version of the character tries to open the door (causing the door handle to rattle), and realising it’s locked, walks away.

But here’s the thing: if time is running backwards for the guy inside his room and opening the door (to find no-one there) why hasn’t he seen the guy outside walking backwards back towards the door and trying the handle?

In other words, time appears to be flowing in different directions by the door – or at least, in different directions for each character.

I think it’s clear by the end of the movie we’ve figured out that it’s the glasses which cause the change of flow direction for time (though whether time actually flows backwards, or that things look like they’re going backwards can be questioned!). Since only one person can wear a single pair of glasses at the same time, it seems reasonable to assume that time is indeed personal and that there is a time bubble or something around our guy. After all – he’s still walking forwards whilst everyone else is walking backwards.

The Perception of Time

The flip side of this is that no matter what direction time flows, we perceive it as forwards – rather like applying a modulus function on time ( -2 seconds becomes 2 seconds).

This already happens in physics; I remember a cretinous teacher who took joy in deducting a mark from me when I was calculating “work done”, given as force times distance. We were told that distance was measured positive from left to right, but in the example the force was applied to an object moving in the opposite direction, so I gave it a negative sign. Of course, this gave me a negative product, but since work done cannot be negative I applied the modulus and gave the final work done as a positive number.

Mr Cretin took a mark away because he didn’t even want to see the negative number in a work done calculation. I still disagree with him. But the point remains – having a closed mind and removing a negative sign completely, or being a budding scientist to be and applying the modulus are just 2 ways in which direction is made a non factor.

So why not with time? Maybe wearing these glasses “opens our eyes”!

(As an aside, you might like to read my guest post on the perception of time and its relevance in time travel on the Theory of Space Time blog.)

Time running backwards

The question of time either being personal and acting under its own rules within personal space, or being perceived to be so, brings me onto my final point – time actually running backwards.

Time travel seems to be obsessed with moving from one point in time to another, but for the large part, time flows in one (forwards) direction. It’s often referred to as the “Arrow of Time” – a term developed by astronomer Arthur Eddington which basically says that there’s an obvious direction or flow of time reference: Wikipedia.

(Sometimes we experience time appearing to move backwards from the viewpoint of a time machine making a backward trip, but I’d suggest that this is little more than illusion – parked cars don’t really move backwards when we walk forwards alongside them, for example.)

So how does physics work when time runs backwards? For example, we saw in the movie a plane flying backwards because time flows backwards. But for the plane to remain in the air, complete with its aerodynamic design, surely physics must have changed to keep it airborne?

To the left is a snapshot of the plane in the sky. It’s not falling, yet it’s not defying gravity. The force of gravity is an acceleration so has a time term, but here in this snapshot time has simply been removed from the equation. Is the gravitational force now working in the opposite direction so keep the plane airborne?

Physical processes at the microscopic level are believed to be either entirely or mostly time-symmetric: if the direction of time were to reverse, the theoretical statements that describe them would remain true. Yet at the macroscopic level it often appears that this is not the case: there is an obvious direction (or flow) of time. Reference: Wikipedia“

In practice, I don’t know what this actually means and how that relates to the (macroscopic) plane, but I wondered further about the sign of time in vector physical equations. For example, velocity. Where speed (a scalar) is concerned only with how fast something goes, velocity is more specific; direction is also important.

Usain Bolt is the fastest human on the planet and ran 100 m in 9.58 seconds (reference: Guinness World Records). (That’s a speed of 10.43 m/s – he can run further in 1 second than he can fall if he fell off a cliff in the same time!) But Usain wouldn’t have won the Olympics unless he ran in the right direction – i.e. from the start line to the finish line. He needed to have the fastest velocity.

Where speed can’t be negative, velocity can (e.g. if Usain ran in the opposite direction). We’re back to my work done calculation here…where we can switch the sign for distance and come up with a negative velocity, can we not equally change the sign of time instead? We’d end up with negative velocity – and it would explain why everyone would be walking backwards…

Personal, perception or actual?

So how is time flowing in Clock Anti-Clock? Is there personal time, is it a matter of perception of time, or does time actually flow backwards?

The more I think about this movie, the more intricacies I find. And getting someone to think can only be a good thing!